I have a rheem classic super quiet 80 furnace that according to
manufacturer's literature, has adjustable air speed that a technician can
adjust. Does anyone know how I can adjust it myself?

http://www.rheemac.com/products/Prod...Category =Gas
Furnaces&SpecificModel=RGLN

Also, if the blower speed is lowered, wouldn't the furnace run hotter and
risk overheating? I hope there is a way to dial down the burners.

I'm not using some rooms and are closing the registers in those rooms to
save energy. This cause the other register to blow stronger, too strong in
fact.

For future reference (when I need to buy a new furnace), does any furnace
maker support home owners directly? I hate to ask the installer for support
since they are not necessarily the most knowledgeable.